The present invention relates to an improvement in the mechanism employed to release fifth wheel coupling devices. More specifically, to an arm and lever mechanism employed with fifth wheel coupling devices which allows an operator to quickly and safely disengage a kingpin of a trailer from the coupler device thereby providing for the separation of a tractor from a trailer and allowing it to be either operated independently or connected to another trailer.
The use of fifth wheels as coupling devices in joining a trailer to a towing vehicle in an articulating manner is very common today. The uses of the fifth wheel in this application ranges from the connection of a recreational trailer to the bed of a pickup truck to the connection of large semi trailers to tractors, a configuration commonly referred to as an over the road truck.
In the case of the latter application, the fifth wheel is commonly made up of a relatively large circular plate-like apparatus that is pivotally mounted to the frame of a tractor in a position that is roughly over the drive wheels. The surface of the fifth wheel is additionally equipped with an open slot that bisects its rearward half. It is this slot in the fifth wheel that provides for the connection of the semi trailer to the tractor.
This connection is facilitated by the use of a kingpin that extends downward from the forward lower surface of the trailer from roughly the center of an additional generally circular plate. The kingpin is a cylindrical apparatus which has the primary function of engaging the fifth wheel. This is accomplished by maneuvering the tractor so that the kingpin passes into the open slot of the fifth wheel. In this procedure, as the kingpin enters the central portion of the fifth wheel, it is engaged by a spring loaded locking jaw apparatus. The kingpin plate then engages the fifth wheel plate in a slidable manner. Additionally, a layer of grease is commonly positioned between the kingpin and fifth wheel plates to ensure their proper operation during use.
This locking apparatus effectively holds the kingpin (and therefore the semi trailer) in the desired location relative to the tractor while allowing the semi trailer to pivot in relation to the tractor. The pivotal nature of the connection afforded by the use of the fifth wheel allows the tractor/trailer configuration to articulate during operation. This ability of the tractor/trailer combination as it allows them to negotiate streets and roads that an unarticulated vehicle of equal length and capacity could not.
The release of the above described connection is accomplished through the use of a drop handle that protrudes from one side of the fifth wheel. The drop handle is connected to the locking jaws and, when engaged, operates to open the lock jaws thereby releasing the kingpin. Once this has been accomplished, the tractor is then free to move off and engage a different semi trailer.
While this system has been employed for a long time with relatively good success, it does suffer from inadequacies most of which result from the design of the release mechanism, the drop handle. The first of these is a direct result of the location of the drop handle on the side of the fifth wheel. The problem of this is one of accessibility. That is to say, because of its location, it can be difficult for the operator of the tractor to reach in commonly over the drive tires and under the trailer and disengage the fifth wheel by the use of the drop handle. This can be difficult in normal circumstances and only becomes more so in adverse weather conditions such as wind, rain, and snow.
Another problem associated with the drop handle is some circumstances can result in the interference with its release function. Typically, the circumstances leading to this are age and wear of the operational components increasing the effort needed to release the lock jaws, dirt and grit also causing the operator to use more force to operate it, and snow and ice jamming the mechanisms or making it difficult to grasp and operate the drop handle. All of the above described deficiencies of the coupling apparatus of the commonly used fifth wheel also present safety concerns as difficulties in the operation and location of the drop handle can lead to accidents resulting in damage or operator injury.
Therefore, it can be seen that it would be desirable to provide a means of releasing the coupling apparatus of a fifth wheel that is easily accessible to the operator and which can be operated in a safe and effective manner either during the day or at night and in all weather conditions.